For the failure of CapXon, I think it might not be their wrong. The problem is OEMs are always seeking lower cost, so they use 85 degrees caps instead of 105 or 125 deg caps. Comparing apples to apples, a CapXon 105 deg cap may not be so bad compared to a "generic use" model chemicon/rubycon.
If we were to ignore the BOM of our customers and use different parts (not necessarily of lower quality), then we'd get a complaint and the customer would send back the shipment. With small, unmarked, components this would not be as conspicuous as with, say, replacing large blue BC/Vishay caps with black Nichicon items....
Having said that, our company once had a logistics manager and director that were always on the look out for cheaper components from the original manufacturer. They didn't shout to the world they were doing that, but before they got fired (inevitably, but it IMHO took too long), I had to deal with far more than average rejects. The time it took us to put this right cost far more than those two morons saved. In the end they got wise and purchased from authorized distributors like Arrow and Avnet and the likes and our problems ended.
Another fail source is ripple current. This heats up the cap, and have the same consequence of underrated temperature, especially in a shitty product designed for cost. Lower inductance, smaller transformer and asynchronous rectification contribute to higher ripple current and higher loss, therefore higher temperature, shorter life.
Of course, using a cap outside of spec will shorten its life, whatever the brand that is on it.
I don't think CapXon can not make good caps, anyway these days it is easy to reverse engineer almost any products, including capacitors from competitors. The reason they make shit for shit is all because of cost.
At least CapXon is a brand that's well known and that has datasheets. That can't be said for the real nasty stuff.
Less scrupulous companies may sell rejects under a different name, I once found out.
I maintain the lighting system in an apartment building, and at the time I was using Philips Genie energy saving lamps. Then I found a department store was selling identical looking ESLs with their own brand on it, priced rather friendlier. These were sourced from Philips as they even carried a little symbol I know to be a Philips factory identifier. They turned out not to be so identical. The light was slightly paler and their failure mode was different.
At EOL, I cracked open the socket to see the ballast. All Philips ballasts were stuffed with Aishi electrolytics (a brand I've come to find in a variety of lighting products used in several brands and which I trust), but the department store's were "Bright". In the Philips ESL, it was the lamp that failed, in the department store's it was the ballast. The main smooting capacitor had burst open on all of them.
I didn't think much of it as the department store's ESLs had exceeded indicated life (specified exactly the same as the Philips ESLs, BTW), but later I discovered almost by accident they were actually carrying the exact same type as the Aishi caps used in the Philips ESLs. My guess, a lower quality or rejected batch dumped on the market under a fantasy brand that Philips deemed good enough to be used in private label stuff.